The invention relates to a data communication system, particularly for a motor vehicle.
The CAN BUS system is an example of a data communication system which is used in motor vehicles for monitoring, connecting, and controlling a plurality of functions. Various control or operational devices are associated with terminal devices which are connected to the bus system, and each contains its own voltage control device for generating an operating voltage from the higher battery voltage of the vehicle's electrical system. During regular operation, the voltages on the data transmission lines of the bus system lie within an operating voltage range; an average constant voltage level is set by way of resistor networks at approximately one half of the operating voltage. The entire data communication process may be interrupted due to short circuiting of a data transmission line to ground potential or to the battery potential, or due to separation of the ground connection of a terminal device.
Separation of the ground connection at only one terminal device can lead to the disruption of the entire data communication process due to a shift of the constant voltage level on the data transmission lines, although the entire communication system would still operate adequately without this one terminal device.